HW-101 QSK Modification T/R Relay Replacement The HW and SB series of transceivers have two 4PDT relays which provide T/R, In this modification, these two relays are replaced by three 2PDT relays. These are DS series relay, part number DS2E-S-DC24V. This document describes how the conversion to faster relays was performed by N4YG. It is intended only as a guide because it is one of many ways that it could have been done. Other than removal of the connections to the original relays and addition of a resistor, nothing is changed or removed from the HW-101. My relays were good, so I left them mounted in the chassis. Three small boards were constructed using Veroboard. These are shown in the block diagram below. The Transmit Relay Board contains only and single DS relay, whereas the Dual-Relay Board contains two. The Relay Driver Board contains the power supply and the control circuitry. The latter 2 boards were located near RL2 and were strapped to the existing cable harness. The small Transmit Relay Board was located near RL1. 12.6 VAC PTT V12B Cathode V12B Grid Relay Driver Board C+ C- Amp Relay Transmit Relay Board Dual-Relay Board P (2) NC (2) NO (2) P (4) NC (4) NO (4) RL1 Previous Connections RL2 Previous Connections
Relay Driver Board All inputs come from V12, which fortunately is located very near RL2. 12.6 VAC from pin 5, Push-To-Talk (PTT) from pin 8 and audio (VOX) from pin 9. Filament voltage is applied to a double and then to a circuit somewhat like a regulator which drops the voltage to 24 to 26 VDC. FET Q2 drives the coils of the relays which, unlike ordinary relays, are polarized. Q2 is turned on by either the PTT or VOX signal. The PTT voltage is a +15 volt cathode bias which is shorted to ground by the mic button during transmit. The VOX signal contains either transmit audio or the CW sidetone taken from the grid of the relay driver tube V12B. When Q2 turns on, not only are the three DS relays are activated, but the output labeled Amp Relay is grounded. This will activated any modern linear amplifier if it is connected. The voltage at this terminal should not exceed 24 volts, which means an unmodified SB-220 cannot be connected here. My SB-220 has a mod in it which allows me to connect it here. This mod is like one commonly referred to as SoftKey. An unmodified older amplifier has higher voltage at its relay terminal, which requires a relay in the controlling transmitter or transceiver. We have chosen the parallel the two switches in the relay on the Transmit Relay Board. In not paralleled, one could be used for linear amp activation as in the original configuration. Getting It Done Again, this is the way I did it. This will describe the procedure, but you may want to use this as a guide to doing it another way. The last page of this document is group of images of the 3 boards. Begin by printing this page, making sure that it is printed at 100% scale. Cut Veroboard to the size shown. Count the holes. Then, referring to the reverse image, mark the places where the copper strips are to be broken. Remove the copper. Mark the board so that you will know which edge is the top. Cut out the overlay image, making them larger than the board. Hold the board up to light and place the overlays on top of the board and make sure you can align the components with the holes in the board. Apply glue (I use a glue stick) to the paper overlays and
glue them to the top of the board. With an awl or ice pick, punch holes where the components go through the boards. Now place the components of the board and carefully solder them in place. Attach wires of sufficient length to the board. Inspect the finished boards to make sure there are no solder bridges. Now that you have the boards completed, you are almost ready to install them in the transceiver. First, it is a good idea to make sure that the power supply on the Relay Driver Board operates properly. Connect wires from 12.6 and GND on the board to pin 5 and the center pin respectively of V12. Being careful not to short anything, turn on the transceiver and check the voltage at C+. It should be between 24 and 27 volts. If all is well proceed. Place the Transmit Relay Board near RL1 and the Dual-Relay Board and the Relay Driver Board near RL1. Refer to the graphic of the old relay pins and also remember that tube pins are numbered in clockwise direction when viewed from the bottom of the board. I recommend that connections to RL1 be removed oneby-one. Connect the wires from the Transmit Relay Board after disconnecting them from RL1 as follows: - C+ and C- to the corresponding points on the Relay Driver Board - P to the ANTENNA jack (pin 1 of RL1) - NO to the transmitter output (pin 5 of RL1) - NC to the receiver input (pin 9 of RL1) Disconnect the GREEN wire attached to pin 14 of RL1. This will disable both RL1 and RL2.
Connect wires from the Relay Driver Board to the adjacent PC board which contains V12 as follows: - C+ and C- to the corresponding points on the Dual-Relay Board - 12.6 to pin 5 of V12 - GND to the center pin of V12 - PTT to pin 8 of V12 - V12B Grid to pin 9 of V12 - RLY to the Amplifier Relay line (only if softkey installed in old amp) Connect wires coming from Dual-Relay Board to wires removed from RL2 as follows: Normally Closed Contacts - NCA 1 - White-Red - NCB 2 White-Yellow-Yellow (2 wires) - NCC 3 White-Red-Red )2 wires) - NCD 4 White-Blue (2 wires) Normally Open Contacts - NOA 5 - Yellow - NOB 6 - Blue (2 wires) - NOC 7 White-Orange-Orange - NOD 8 White=Violet-Violet (2 wires) Poles - PA 9 White-Blue-Blue - PB 10 - Ground - PC 11 White-Orange - PD 12 White-Green One final thing and you are done. Connect a 470K resistor across R903, that is, in parallel with it. It is a 2.3 M resistor connected to the VOX DELAY pot located on the rail along the side of the chassis. The thresholds are a bit different in the new system and this allows shorter delays in the VOX circuit. Test it. It should be good to go, and nice.